The problem with high school shop classes are that you need a large block if time in the middle of setting up and cleaning up. Chess pieces are nice projects that can be done in short enough time blocks. Many of the pieces offer curves and straight lines that can be made into pretty simple G-code programs.
IF you have a GOOD crew, you might break things down into three or four teams and open things up to a class project, where each team is responsible for a few parts of an assembly. There is a very simple bench mounted one lung primitive single cylinder engine floating around the net. Base plate, cylinder, a simple crank, connecting rod, cam, and flywheel. The ignition fires off of a old set of chevy points, coil, and total loss battery power.
Ways to get past possible problem areas are to use an old weed whacker motor for parts. If the crank seems too complex for your level of students, use an old WW crank. It also has a taper for the flywheel.
There are several reasons for the small gas motor as a shop project. It opens their minds to a slew of possibilities. Internal combustion principal two stroke/four stroke, electricity/electronics/science/physics, CAD/CAM/math/fits/finishes, time planning.... ahhh, makes me passionate. Loved Shop, would love to each it.